Hydrogen-Bond-Assisted Chalcogen Transfer between Phosphine Selenides and Arsine Oxides

TL;DR

This paper reports a new method for synthesizing arsine selenides using hydrogen-bond-assisted chalcogen transfer under mild conditions.

Contribution

The first example of H-bond-assisted chalcogen exchange between arsine oxides and phosphine selenides is demonstrated.

Findings

The reaction works in both protic and aprotic solvents and is accelerated by nonaqueous acids.

Bulky substituents on reagents hinder the reaction efficiency.

A four-membered cyclic transition state is involved in the reaction mechanism.

Abstract

The Brønsted
acid catalysis is widely regarded as
one of the
most effective methods for activating inert substrates and enabling
unique reactivity. In this work, we introduce the first example of
H-bond-assisted chalcogen exchange between arsine oxides and phosphine
selenides under mild conditions, providing a powerful approach to
the synthesis of arsine selenides. The reaction proceeds successfully
in both protic and aprotic solvents and is accelerated by the presence
of any nonaqueous acid. This newly discovered reaction is tested for
various arsine oxides R3AsO (R = Ph, Et, nBu, iPr) and phosphine selenides R3PSe
(R = Ph, Me, Et, tBu) and overall demonstrates high
conversion, although the use of reagents with bulky substituents significantly
hinders its efficiency. The reaction mechanism involves the formation
of a four-membered cyclic transition state, which requires overcoming
steric and electrostatic repulsion, as well as significant distortion
of the reagents’ tetrahedral geometry. Hydrogen bonding with
the As=O fragment helps to reduce electrostatic repulsion between
the P=Se and As=O groups, making the formation of the
cyclic intermediate more favorable.

The Brønsted
acid catalysis is widely regarded as one
of the most effective methods for activating inert substrates and
enabling unique reactivity.

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